The listing or discussion of background information or an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the information or document is part of the state of the art or is common general knowledge.
(Hydro)halocarbons are typically used as refrigerant or propellant materials. Over the last 20 years, the variety of (hydro)halocarbons used in these applications has changed in view of environmental concerns.
Dichlorodifluoromethane (refrigerant R-12) possesses a suitable combination of desirable refrigerant properties, and was for many years the most widely used refrigerant. Due to international concern that fully and partially halogenated chlorofluorocarbons were damaging the earth's protective ozone layer, there was general agreement that their manufacture and use should be severely restricted and eventually phased out completely. The use of dichlorodifluoromethane was phased out in the 1990's.
1,1,1,2-tetrafluoroethane (R-134a) was introduced as an alternative replacement refrigerant for R-12, particularly for mobile air-conditioning. However, despite having no significant ozone depletion potential, R-134a has a global warming potential (GWP) of 1300.
In response to this, (hydro)fluoroolefins are increasingly being considered as working fluids in applications such as refrigeration, heat pumping, foam blowing, propellants and flame retardants. 2,3,3,3-tetrafluoropropene (R-1234yf), which has a GWP of 4, has been identified as a candidate alternative refrigerant to replace R-134a in certain applications, notably in mobile air-conditioning or heat pumping applications.
As the next generation of low-GWP (hydro)fluoroolefins are adopted across a wide range of systems, mixtures of (hydro)fluoroolefins and previous refrigerants, such as R-134a, are expected to occur during the recovery and recycling of refrigerants. For example, contamination of a (hydro)fluoroolefin with R-134a may be expected when the (hydro)fluoroolefin is used in a system which previously utilised R-134a.
The comparatively higher cost and reduced availability of such (hydro)fluoroolefins makes the ability to separate such mixtures desirable. For example, in certain applications (e.g. mobile air-conditioning) it may not be tolerable or permissible to return a low-GWP component to a system if it is contaminated with significant levels of high-GWP refrigerant, i.e. R-134a.
However, the separation of such (hydro)fluoroolefins from undesired halogenated ethanes and methanes can be difficult and unattractive. For example, R-134a forms a minimum boiling azeotrope with R-1234yf, making distillation difficult. As the composition of such an azeotrope varies to some extent with system pressure, a twin column distillation system could be employed in order to separate the two components. However, such a system would be very expensive to build, and complex to operate. The use of a complex distillation system is also not an attractive option for the wider refrigerant supply chain, such as use by service contractor companies or refrigerant distributors.
The subject invention addresses the above deficiencies by providing a means for such a separation.